Defender, no video on screen

[rogerxy]

I bought a Defender some time ago which was a DOA.

I have recapped all cards which made the G07 monitor alive again but still nothing on the screen. (I got video on the screen when I tried with another game so I know the monitor is working)

I've done som work with the PCB:s as well:

- Changed to a switched power supply (from arcadeshop), just to get the regular PS out of the equation

- Changed the ROM Board Ribbon Cable (to the one from arcadeshop)



- Changed the 4116 RAMs to 4164, as well as the 4164 adapter from arcadeshop



- Checked all ROM:s (all are OK)



Despite this, the problem is the same as it was before I did all of the above

I get raster on my monitor, but it shows nothing. The 4 LEDs on the ROM board are fully lit (no blinking) from the second I start the game.



+5V, -5V and 12V all seem to be ok

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So, my question is, could anyone help me where I continue my trouble shooting. I am unfortunately stuck as of now

Thank you very much in advance

[rogerxy]

[Ramakers]

Have you any means of checking the signals on the boards? I think the CPU doesn't start. That's why the test LED's don't blink.
First I would check the clock signals (pg12) and the reset circuit (pg9) the manual can be found on the KLOV http://www.klov.net/manuals-videogames/D/Defender.pdf

[rogerxy]

I have a logic probe. I'm not that familiar with but I will give it a try, thank you for your advice, I will get back with my results

[rogerxy]

The clock generator crystal gives PULSE on one leg and LOW on the other leg, so I guess that works

Do you mean the CPU on the main board or the ROM board? I've found pulse on both of them but not sure exactly where I shall look though 

[Ramakers]

Has been a while since I had a defender on the bench, does it have a CPU on the ROM board?
Anyhow start with the main CPU on the main board. The MC6809 located at 2I. Here is the datasheet:
http://www.gbgmv.se/dl/doc/md09/MC6809_DataSheet.pdf

Look for activity at the address and data pins.

On the other hand, what game did you use to check the monitor?